Hydrophobically and Cationically Modified Relative Permeability Modifiers and Associated Methods

ABSTRACT

Methods comprising providing a relative permeability modifier that comprises a hydrophilic polymer backbone with a hydrophobic modification and incorporating at least one cationic compound onto the hydrophilic polymer backbone. The hydrophilic polymer is one or more of: a polyacrylamide; a polyvinylamine; a poly(vinylamine/vinyl alcohol); an alkyl acrylate polymer; cellulose; chitosan; a polyamide; a polyetheramine; a polyhydroxyetheramine; a polylysine; a polysulfone; a gum; or a starch. The hydrophobic modification is achieved either by reacting the hydrophilic polymer with a hydrophobic compound or by a polymerization reaction product of a hydrophilic monomer and a hydrophobically modified hydrophilic monomer. The hydrophobic compound has an alkyl chain length from 4 to 22 carbons and is one or more of: an alkyl acrylate; an alkyl methacrylate; an alkyl acrylamide; an alkyl methacrylamide; or an alkyl dimethylammoniumethyl methacrylate halide.

BACKGROUND

The present invention relates to subterranean treatments and, moreparticularly, in one or more embodiments, to introducing ahydrophobically and cationically modified relative permeability modifierinto a subterranean interval to reduce the effective permeability of thesubterranean interval to aqueous-based fluids.

The production of water with hydrocarbons, oil and/or gas, from wellsconstitutes a major problem and expense in the production of thehydrocarbons. While hydrocarbon producing wells are usually completed inhydrocarbon producing formations, the formations frequently containlayers of water or may be located adjacent to water producing zones. Thehigh mobility of the water often allows it to flow into the wellbore byway of natural fractures and/or high permeability streaks present in theformation. Over the life of such wells, the ratio of water tohydrocarbons recovered often becomes so high that the cost of producingthe water, separating it from the hydrocarbons and disposing of itrepresents a significant economic loss.

Chemicals referred to as relative permeability modifiers have beenutilized to decrease the production of water with hydrocarbons. That is,water permeability modifying chemicals such as polyacrylamide have beenintroduced into hydrocarbon and water producing formations so that thechemicals attach to adsorption sites on surfaces within the porosity ofthe formations. The presence of the chemicals in the formations has theeffect of reducing the flow of water through the formations. The use ofwater permeability modifying chemicals in hydrocarbon and waterproducing formations to decrease the production of water involves lessrisk than other techniques such as blocking the flow of water withcross-linked polymers, and has the advantage that they do not requireexpensive zonal isolation techniques. However, the use of hydrophilicwater permeability modifying chemicals, e.g., polyacrylamides, haveheretofore resulted in only small temporary reductions in waterproduction and/or unacceptable levels of reduction in hydrocarbonproduction.

Hydrophobically modified polymers have recently been used as relativepermeability modifiers. Hydrophobically modified polymers may also beused in operations to assist in leak off control, clay stabilization,fines control, cement fluid loss control, and the diversion of treatmentfluids. However, under certain pH and temperature conditions (e.g., attemperatures above 140° F. and at pH's above 7) these polymers mayprecipitate out of solution limiting their effectiveness as relativepermeability modifiers.

Thus, improvements are necessary in the methods and compositions used toreduce water permeability in water and hydrocarbon producingsubterranean formations. Additionally, improved formation stimulationmethods capable of stimulating production while also reducing theproduction of water from a formation with temperatures above 140° F.and/or while using treatment fluids that have pH's above 7 arenecessary.

SUMMARY

The present invention relates to subterranean treatments and, moreparticularly, in one or more embodiments, to introducing ahydrophobically and cationically modified relative permeability modifierinto a subterranean interval to reduce the effective permeability of thesubterranean interval to aqueous-based fluids.

In one embodiment, the present invention includes a method ofintroducing a hydrophobically and cationically modified relativepermeability modifier into a portion of a subterranean formation,wherein the hydrophobically and cationically modified relativepermeability modifier comprises a hydrophilic polymer backbone with ahydrophobic modification and a cationic modification.

In another embodiment, the present invention provides a method ofimproving the stability of a relative permeability modifier comprising:providing a relative permeability modifier that comprises a hydrophilicpolymer backbone with a hydrophobic modification; and incorporating atleast one cationic compound onto the hydrophilic polymer backbone toform a hydrophobically and cationically modified relative permeabilitymodifier.

In another embodiment, the present invention includes a treatment fluidcomprising a hydrophobically and cationically modified relativepermeability modifier that comprises a hydrophilic polymer backbone witha hydrophobic modification and a cationic modification.

The features and advantages of the present invention will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to subterranean treatments and, moreparticularly, in one or more embodiments, to introducing ahydrophobically and cationically modified relative permeability modifierinto a subterranean interval to reduce the effective permeability of thesubterranean interval to aqueous-based fluids.

Embodiments of the present invention relate to using a hydrophobicallyand cationically modified relative permeability modifier to treat asubterranean formation, or an interval or portion thereof. As used inthis disclosure, the term “relative permeability modifier” refers to awater-soluble polymer comprising a hydrophilic polymer backbone thatselectively reduces the effective permeability of at least a portion ofa subterranean formation to aqueous-based fluids. As used in thisdisclosure, the terms “hydrophobically modified,” “hydrophobicmodification,” and the like refer to the incorporation into thehydrophilic polymer backbone of at least one hydrophobic group, whereinthe alkyl chain length is about 4 to about 22 carbons. As used in thisdisclosure, the terms “cationically modified,” “cationic modification,”and the like refer to the incorporation of at least one cationic groupor a cationic forming group that comprises a short chain alkyl group,wherein the alkyl chain length is about 1 to about 3 carbons. As used inthis disclosure, the term “hydrophobically and cationically modifiedrelative permeability modifier” refers to a relative permeabilitymodifier that has both a hydrophobic modification and a cationicmodification. There may be several potential advantages to the methodsand compositions of the present invention, only some of which may bealluded to herein. One of the many potential advantages of the methodsand compositions of the present invention is that the hydrophobicallyand cationically modified relative permeability modifiers of the presentinvention may remain in solution at temperatures above 140° F. and pH'sabove 7.

In accordance with certain embodiments of the present invention, thehydrophobically and cationically modified relative permeability modifiermay form a hydrated or hydratable film or a mono- or multi-layeredadsorbed hydrated or hydratable polymer layer on a well bore surfaceand/or around an oil droplet in a pore space, including pore throats inthe interval of the subterranean formation, thereby decreasing waterpermeability. The hydrophobically and cationically modified relativepermeability modifier may also be used to divert treatment fluids, forexample, to less permeable portions of the formation. Additionally, thehydrophobically and cationically modified relative permeability modifiermay also be used in cementing operations, fracturing operations, anddrilling operations and also may be used as a spacer fluid.

In general, suitable hydrophobically and cationically modified relativepermeability modifiers may be any of a variety of water soluble polymersthat are both hydrophobically modified and cationically modified and arecapable of selectively reducing the effective permeability of aformation to aqueous-based fluids without a comparable reduction of theformation's effective permeability to hydrocarbons. While thehydrophobically and cationically modified relative permeabilitymodifiers suitable for use in the present invention may have hydrophobicgroups incorporated into the hydrophilic polymer structure, they shouldremain water soluble. As used in this disclosure, “water soluble” refersto at least about 0.0001 weight percent soluble in water. In certainembodiments, the water-soluble polymer is at least about 0.45 weightpercent soluble in distilled water at room temperature. In certainembodiments, the water-soluble polymer is at least about 0.6 weightpercent soluble in distilled water at room temperature.

The hydrophobically and cationically modified relative permeabilitymodifiers of the present invention have a cationic charge as a result ofa cationic modification. It should be noted that the cationic charge inthe polymer is independent of the pH of the fluid comprising therelative permeability modifier. In other words, in some embodiments, thecationic modification comprises a quaternized nitrogen, and not aprotonated amine as would be the case if an amine is contacted with aBronsted acid or a Lewis acid reacted amine. Therefore, the cationiccharge is not because acidification or protonation of an amine.Furthermore, it is believed that the incorporation of a cationicmodification into the hydrophilic polymer structure increases the chargeof the hydrophobically and cationically modified relative permeabilitymodifier, allowing these compounds to remain in solution at temperaturesabove 140° F. and pH's above 7.

Examples of hydrophobically and cationically modified relativepermeability modifiers may comprise a hydrophilic polymer backbone, atleast one hydrophobic modification, and at least one cationicmodification. In some embodiments, the hydrophobic modificationcomprises a hydrophobic branch comprising an alkyl chain of about 4 toabout 22 carbons and the cationic modification comprises a cationicgroup or cationic forming group comprising an alkyl chain of about 1 toabout 3 carbons. In certain embodiments, the hydrophobic branch may havean alkyl chain length of about 7 to about 22 carbons. In certainembodiments, the hydrophobic branch may have an alkyl chain length ofabout 12 to about 18 carbons. In certain embodiments, the cationic groupor cationic forming group may have an alkyl chain length of about 1, 2,or 3 carbons. In certain embodiments, the hydrophobically andcationically modified relative permeability modifiers may comprise apolymer backbone that comprises polar heteroatoms. Generally, the polarheteroatoms present within the polymer backbone of the hydrophobicallyand cationically modified relative permeability modifiers include, butare not limited to, oxygen, nitrogen, sulfur, or phosphorous.

Hydrophobically and cationically modified relative permeabilitymodifiers suitable for use in the present invention may be synthesizedutilizing any suitable technique. In certain embodiments, suitablehydrophobically and cationically modified relative permeabilitymodifiers may be synthesized by the hydrophobic modification and thecationic modification of a hydrophilic polymer via a reaction with ahydrophobic compound and a cationic compound. As used herein, the term“cationic compound” includes not only cationic compounds, but cationicforming compounds. For example, in one embodiment, suitablehydrophobically and cationically modified relative permeabilitymodifiers may be a reaction product of a reaction comprising ahydrophilic polymer, a hydrophobic compound, and a cationic compound. Inanother embodiment, the hydrophobically and cationically modifiedrelative permeability modifiers may be prepared by reacting a reactionproduct formed from a reaction of a hydrophilic polymer with ahydrophobic compound, with a cationic compound. In yet anotherembodiment, the hydrophobically and cationically modified relativepermeability modifiers may be prepared by reacting a reaction productformed from a reaction of a hydrophilic polymer with a cationiccompound, with a hydrophobic compound. In yet another embodiment, thehydrophobically and cationically modified relative permeabilitymodifiers may be prepared from a polymerization reaction comprising ahydrophilic monomer, a hydrophobically modified hydrophilic monomer, anda cationic monomer. In certain embodiments, the hydrophobically andcationically modified relative permeability modifiers may be pre-reactedbefore they are placed into the well bore. Alternatively, in someembodiments, the hydrophobically and cationically modified relativepermeability modifiers may be prepared by an appropriate in situreaction. Hydrophobically modified polymers and methods for theirpreparation are described in more detail in U.S. Pat. Nos. 6,476,169 and7,117,942, the disclosures of which are incorporated herein byreference. Those of ordinary skill in the art, with the benefit of thisdisclosure, will be able to determine other suitable methods for thesynthesis of suitable hydrophobically and cationically modified relativepermeability modifiers.

As mentioned above, in one embodiment, hydrophobically and cationicallymodified relative permeability modifiers suitable for use in the presentinvention may be synthesized by the reaction of a hydrophilic polymerwith a hydrophobic compound and a cationic compound. Hydrophilicpolymers suitable for forming the hydrophobically and cationicallymodified relative permeability modifiers of the present invention shouldbe capable of reacting with hydrophobic compounds and cationiccompounds. Examples of suitable hydrophilic polymers include, homo-,co-, or terpolymers such as, but not limited to, polyacrylamides,polyvinylamines, poly(vinylamines/vinyl alcohols), alkyl acrylatepolymers, alkylamino acrylate or alkylamino alkylacrylate polymers ingeneral, and combinations thereof. Additional examples of alkyl acrylatepolymers, polyacrylamides, and alkylamino acrylate polymers andalkylaminoalkyl acrylate polymers include polydimethylaminoethylmethacrylate, polydimethylaminopropyl methacrylamide,poly(acrylamide/dimethylaminoethyl methacrylate), poly(methacrylicacid/dimethylaminoethyl methacrylate), poly(2-acrylamido-2-methylpropane sulfonic acid/dimethylaminoethyl methacrylate),poly(acrylamide/dimethylaminopropyl methacrylamide), poly (acrylicacid/dimethylaminopropyl methacrylamide), poly(methacrylicacid/dimethylaminopropyl methacrylamide), and combinations thereof.

In certain embodiments, a hydrophilic polymer suitable for use in thepresent invention may comprise a polymer backbone that contains areactive amino group in the polymer backbone or as a pendant group,wherein the reactive amino group is capable of reacting with ahydrophobic compound and/or a cationic compound. In some embodiments, asuitable hydrophilic polymer may comprise a dialkyl amino pendant group.In some embodiments, a suitable hydrophilic polymer may comprise adimethyl amino pendant group and a monomer comprising dimethylaminoethylmethacrylate or dimethylaminopropyl methacrylamide. In some embodiments,a suitable hydrophilic polymer may be formed from monomers containingamine groups in about 20-100 mole % of the monomers. In certainembodiments, a suitable hydrophilic polymer may comprise a polymerbackbone comprising polar heteroatoms, wherein the polar heteroatomspresent within the polymer backbone of the hydrophilic polymer includesoxygen, nitrogen, sulfur, or phosphorous. Suitable hydrophilic polymersthat comprise polar heteroatoms within the polymer backbone includehomo-, co-, or terpolymers, such as, but not limited to, celluloses,chitosans, polyamides, polyetheramines, polyethyleneimines,polyhydroxyetheramines, polylysines, polysulfones, gums, starches, andcombinations thereof. In one embodiment, the starch is a cationicstarch. A suitable cationic starch may be formed by reacting a starch,such as corn, maize, waxy maize, potato, tapioca, or the like, with thereaction product of epichlorohydrin and trialkylamine.

Suitable hydrophobic compounds that are capable of reacting with thehydrophilic polymers include alcohols, amines, epoxides, alkyl halides,sulfonates, sulfates, organic acids, and organic acid derivatives thatcomprise an alkyl chain length of from about 4 to about 22 carbons.Examples of suitable organic acids and derivatives thereof include, butare not limited to, acid anhydrides, esters, imides, acid halides andamides of carboxylic acids that comprise an alkyl chain length of fromabout 4 to about 22 carbons. In another embodiment, the hydrophobiccompounds may have an alkyl chain length of from about 7 to about 22carbons. In another embodiment, the hydrophobic compounds may have analkyl chain length of from about 12 to about 18 carbons. For example,where the hydrophobic compound is an alkyl halide, the reaction betweenthe hydrophobic compound and hydrophilic polymer may result in thequaternization of at least some of the hydrophilic polymer amino groupswith an alkyl halide, wherein the alkyl chain length is from about 4 toabout 22 carbons.

Suitable cationic compounds that are capable of reacting with thehydrophilic polymers include alcohols, amines, epoxides, alkyl halides,sulfonates, sulfates, organic acids, and organic acid derivatives thatcomprise an alkyl chain length of from about 1 to about 3 carbons.Examples of suitable organic acids and derivatives thereof include, butare not limited to, acid anhydrides, esters, imides, acid halides andamides of carboxylic acids that comprise an alkyl chain length of fromabout 1 to about 3 carbons. In another embodiment, the cationiccompounds may have an alkyl chain length of 1, 2, or 3 carbons. Forexample, where the cationic compound is an alkyl halide, the reactionbetween the cationic compound and hydrophilic polymer may result in thequaternization of at least some of the hydrophilic polymer amino groupswith an alkyl halide, wherein the alkyl chain length is from about 1 toabout 3 carbons. Additional examples of suitable cationic compoundsinclude aminoethyltrimethylammonium halides, 2-chloro- or2-bromoethyltrimethylammonium halide, 3-chloro- or 3-bromopropyltrimethylammonium halide and a reaction product of trialkylamine, forexample trimethylamine, with epichlorohydrin.

In some embodiments, a cationic modification and/or a hydrophobicmodification may be incorporated into the hydrophilic polymer backboneby quaternizing amine groups located in the hydrophilic polymerbackbone. In certain embodiments, hydrophobic compounds may be presentin the hydrophilic polymer structure in an amount sufficient toquaternize up to and including about 10% of the amine groups. In certainembodiments, hydrophobic compounds may be present in the hydrophilicpolymer structure in an amount sufficient to quaternize about 1% toabout 5% of the amine groups. In certain embodiments, cationic compoundsmay be present in the hydrophilic polymer structure in an amountsufficient to quaternize up to and including about 50% of the aminegroups. In some embodiments, the cationic compounds may be present inthe hydrophilic polymer structure in an amount sufficient to quaternizeabout 1% to about 20% of the amine groups. In other embodiments, thecationic compounds may be present in the hydrophilic polymer structurein an amount sufficient to quaternize about 5% to about 10% of the aminegroups.

Additional examples of suitable hydrophobically and cationicallymodified relative permeability modifiers include a polymer that has beenhydrophobically modified with an alkyl group present on an amino group(in the polymer backbone or as a pendant group) in quaternized form andhas been cationically modified with an alkyl group present on an aminogroup (in the polymer backbone or as a pendant group) in quaternizedform. For example, an alkyl group may be present on a dialkyl aminopendant group in quaternized form. In one embodiment, the dialkyl aminopendant group comprises a dimethyl amino pendant group. One specificexample of a hydrophobically and cationically modified relativepermeability modifier includes a poly(dimethylaminoethylmethacrylate) orpoly(dimethylaminopropylmethacrylamide) that has been hydrophobicallymodified with an alkyl group with 4 carbons to 22 carbons (e.g., 4carbons, 6, carbons, 8 carbons, 10 carbons, 12 carbons, 14 carbons, 16carbons, 18 carbons, 20 carbons, 22 carbons, etc.) on a dimethylaminogroup and has been cationically modified with an alkyl group with 1 to 3carbons on another dimethylamino group.

As previously mentioned, in certain embodiments, suitablehydrophobically and cationically modified relative permeabilitymodifiers also may be prepared from a polymerization reaction comprisinga hydrophilic monomer, a hydrophobically modified hydrophilic monomer,and a cationic monomer. In another embodiment, suitable hydrophobicallyand cationically modified relative permeability modifiers may beprepared by first polymerizing a hydrophilic polymer and ahydrophobically modified hydrophilic monomer, and then reacting theresulting polymer with a cationic compound or a cationic monomer. In yetanother embodiment, suitable hydrophobically and cationically modifiedrelative permeability modifiers may also be prepared by firstpolymerizing a hydrophilic monomer and cationic monomer, and thenreacting the resulting polymer with a hydrophobic compound orhydrophobic monomer. Suitable hydrophobically and cationically modifiedrelative permeability modifiers synthesized from the polymerizationreactions may have estimated molecular weights in the range of fromabout 100,000 to about 10,000,000. In some embodiments, the mole ratiosof the hydrophilic monomer(s) to the hydrophobically modifiedhydrophilic monomer(s) and the cationically modified hydrophilicmonomer(s) may be in the range of from about 99.98 to 90:10.

A variety of hydrophilic monomers may be used to form thehydrophobically and cationically modified relative permeabilitymodifiers useful in the present invention. Examples of suitablehydrophilic monomers include, but are not limited to, acrylamide,2-acrylamido-2-methyl propane sulfonic acid, N,N-dimethylacrylamide,vinyl pyrrolidone, dimethylaminoethyl methacrylate, acrylic acid,dimethylaminopropylmethacrylamide, vinyl amine, vinyl acetate,methacrylamide, hydroxyethyl acrylate, vinyl sulfonic acid, vinylphosphonic acid, methacrylic acid, vinyl caprolactam, N-vinylformamide,N,N-diallylacetamide, itaconic acid, and styrene sulfonic acid, andcombinations thereof.

A variety of hydrophobically modified hydrophilic monomers also may beused to form the hydrophobically and cationically modified relativepermeability modifiers useful in the present invention. Examples ofsuitable hydrophobically modified hydrophilic monomers include, but arenot limited to, alkyl acrylates, alkyl methacrylates, alkyl acrylamides,alkyl methacrylamides, wherein the alkyl groups have from about 4 toabout 22 carbon atoms. In another embodiment, the alkyl groups have fromabout 7 to about 22 carbons. In another embodiment, the alkyl groupshave from about 12 to about 18 carbons. In certain embodiments, thehydrophobically modified hydrophilic monomer comprises 2-ethylhexylmethacrylate, or hexadecyl methacrylamide. In one embodiment, thehydrophobically modified hydrophilic monomers may be cationic. Examplesof cationic hydrophobically modified hydrophilic monomers include, alkyldimethylammoniumethyl methacrylate halides, and alkyldimethylammoniumpropyl methacrylamide halides. Specific examples of suchmonomers include, octadecyldimethylammoniumethyl methacrylate bromide,hexadecyldimethylammoniumethyl methacrylate bromide, andhexadecyldimethylammoniumpropyl methacrylamide bromide.

A variety of cationic monomers also may be used to form thehydrophobically and cationically modified relative permeabilitymodifiers useful in the present invention. Examples of suitable cationicmonomers include, but are not limited to, dimethyldiallyl ammoniumhalide, trimethylammoniumethyl methacrylate halide,trimethylammoniumpropyl methacrylamide halide,methacrylamidoethyltrimethyl ammonium halide, quaternary saltderivatives of acrylamide and quaternary salt derivatives of acrylicacid and combinations thereof.

In some embodiments, the mole ratio of cationic modifications tohydrophobic modifications present in the hydrophobically andcationically modified relative permeability modifiers may be in therange of from about 1:1 to about 50:1. In other embodiments, the moleratio of cationic modifications to hydrophobic modifications present inthe hydrophobically and cationically modified relative permeabilitymodifiers may be in the range of from about 2:1 to about 20:1. In otherembodiments, the mole ratio of cationic modifications to hydrophobicmodifications present in the hydrophobically and cationically modifiedrelative permeability modifiers may be in the range of from about 5:1 toabout 10:1.

Examples of suitable hydrophobically and cationically modified relativepermeability modifiers that may be utilized include, but are not limitedto:

-   an acrylamide/octadecyldimethylammoniumethyl methacrylate    bromide/trimethylammoniumpropylmethacrylamide terpolymer,-   a dimethylpropylammoniumethylmethacrylate/vinyl    pyrrolidone/hexadecyldimethylammoniumethyl methacrylate bromide    terpolymer,-   an aminoalkyl methacrylate/trialkyl ammonium alkyl methacrylate    halide terpolymer, including a dimethylaminoethyl    methacrylate/alkyldimethylammoniumethyl    methacrylate/trialkylammoniumethyl methacrylate halide terpolymer    and a dimethylaminoethyl methacrylate/hexadecyldimethylammoniumethyl    methacrylate/dimethylpropylethyl methacrylate bromide terpolymer.

In accordance with some embodiments, hydrophobically and cationicallymodified relative permeability modifiers may be present in apermeability modifying fluid introduced into a subterranean formation.Treatment fluids comprising hydrophobically and cationically modifiedrelative permeability modifiers will be referred to herein as“permeability modifying fluids.” Sufficient concentrations ofhydrophobically and cationically modified relative permeabilitymodifiers should be present in these permeability modifying fluids toprovide the desired level of permeability modification. In someembodiments, hydrophobically and cationically modified relativepermeability modifiers may be present in these permeability modifyingfluids in an amount in the range of from about 0.02% to about 10% byweight of the permeability modifying fluid. In another embodiment,hydrophobically and cationically modified relative permeabilitymodifiers may be present in these permeability modifying fluids in anamount in the range of from about 0.05% to about 1.0% by weight of thepermeability modifying fluid. In certain embodiments, hydrophobicallyand cationically modified relative permeability modifiers may beprovided in a concentrated aqueous solution prior to its combinationwith the other components necessary to form the permeability modifyingfluids.

In addition to hydrophobically and cationically modified relativepermeability modifiers, the permeability modifying fluids generally alsocomprise water. The water included in the permeability modifying fluidmay include freshwater, saltwater (e.g., water containing one or moresalts dissolved therein), brines (e.g., natural or produced brines),seawater, or another other aqueous fluid that does not undesirablyeffect the other components in the permeability modifying fluid.

The compositions disclosed herein may be used to treat an interval of asubterranean formation penetrated by a well bore. The interval mayrepresent an interval that has been identified for treatment with ahydrophobically and cationically modified relative permeability modifierto reduce the effective permeability of the interval to aqueous-basedfluids, in accordance with present embodiments. As will be appreciatedby those of ordinary skill in the art, with the benefit of thisdisclosure, the interval may be any interval of a subterranean formationsuitable for treatment. Moreover, as those of ordinary skill in the artwill appreciate, with the benefit of this disclosure, embodiments of thepresent invention may be applicable for the treatment of both productionand injection wells. Additionally, embodiments of the present inventionalso may be suitable for cased well bores or openhole well bores.

In accordance with some embodiments of the present invention, theinterval may be contacted with a hydrophobically and cationicallymodified relative permeability modifier. In some embodiments, thehydrophobically and cationically modified relative permeability modifiermay be present in a permeability modifying fluid introduced into theinterval. In some embodiments, the near well bore portion of theinterval is contacted with the hydrophobically and cationically modifiedrelative permeability modifier. Those of ordinary skill in the art willunderstand that the “near well bore portion” of a formation generallyrefers to the portion of a subterranean formation surrounding a wellbore. For example, the “near well bore portion” may refer to the portionof the formation surrounding a well bore and having a depth ofpenetration of from about 7 to about 10 feet.

Any suitable technique may be used for introduction of the permeabilitymodifying fluid into the interval, for example, bull heading, coiltubing, jointed pipe (e.g., with straddle packers, pinpoint injectiontools, etc.) or any other suitable technique may be used. It should benoted that in some embodiments, to reduce the potential for theundesired fracturing of the interval, the permeability modifying fluidmay be introduced into the interval at matrix flow rates. Example flowrates for the permeability modifying fluid are in the range of fromabout 0.25 barrels to about 3 barrels per minute. However, those ofordinary skill in the art will appreciate that these flow rates aremerely examples, and embodiments of the present invention are applicableto flow rates outside these ranges.

The permeability modifying fluids of the present invention may be usedin a variety of well operations, including fracturing operations,cementing operations, drilling operations, and may also be used asspacer fluids.

In some embodiments, the permeability modifying fluids of the presentinvention may be used in a fracturing operation. In one embodiment, thepresent invention provides a method of fracturing a subterraneanformation penetrated by a well bore, the method comprising introducing afracturing fluid comprising a permeability modifying fluid into the wellbore at or above a pressure sufficient to create or enhance at least onefracture in the subterranean formation. Introducing the fracturing fluidinto the well bore may be accomplished by using any fracturing equipmentknown in the art.

In some embodiments, the permeability modifying fluids of the presentinvention may be used in a drilling operation. In one embodiment, thepresent invention provides a method of drilling a portion of a well borecomprising the steps of providing a drilling fluid that comprises apermeability modifying fluid and drilling the well bore. Drilling thewell bore may be accomplished by using drilling equipment, such as adrill string and a drill bit, along with the drilling fluid. Drillingoperations may include any suitable technique for forming a well borethat penetrates a subterranean formation. Examples of suitabletechniques for forming a well bore may include, but are not limited to,rotary drilling and cable-tool drilling. Other techniques for forming awell bore may be used, but generally to a lesser extent. Rotary drillingoperations typically involve attaching a drill bit on a lower end of adrill string to form a drilling tool and rotating the drill bit alongwith the drill string into a subterranean formation to create a wellbore through which subsurface formation fluids may be produced. As thedrill bit penetrates the subterranean formation, additional joints ofpipe may be coupled to the drill string. In another method of drilling,coiled tubing may be used instead of jointed pipe and the drill bit maybe rotated using a downhole motor.

In some embodiments, the permeability modifying fluids of the presentinvention may be used in a cementing operation. In one embodiment thecementing operation may be a primary cementing operation. In oneembodiment, the present invention provides a method comprising providinga cement composition that comprises a hydrophobically and cationicallymodified relative permeability modifier, introducing the cementcomposition to a subterranean well bore; and allowing the cementcomposition to set therein. In another embodiment, the cementcomposition may be pumped into the annular space between the walls of awell bore and the exterior surface of the pipe string disposed therein.The cement composition may be permitted to set in the annular space,thereby forming an annular sheath of hardened substantially impermeablecement therein that substantially supports and positions the pipe stringin the well bore and bonds the exterior surfaces of the pipe string tothe walls of the well bore. In another embodiment, the cementcomposition may be used in remedial cementing operations such asplugging highly permeable zones or fractures in well bores, pluggingcracks in holes in pipe strings, and the like.

In some embodiments, spacer fluid compositions comprising a permeabilitymodifying fluid of the present invention are provided. In oneembodiment, the spacer fluid may be utilized as a buffer between twofluids during subterranean operations. For example, in some embodiments,a spacer fluid may be pumped into a well bore between a first fluid anda second fluid. The first fluid should be displaced with the spacerfluid, and the spacer fluid should be displaced with the second fluid.Among other things, the spacer fluids should be compatible with thefluid that it is displacing and the second fluid that is displacing thespacer fluid, in that there should be no undesirable interactionsbetween the spacer fluid and the first or the second fluid. Generally,the first fluid may be any fluid that the spacer fluid should displace,such as drilling fluids. The second fluid may be any fluid desired to beintroduced into the well bore, such as cement compositions, drillingfluids, completion brines, and the like. For example, during a drillingfluid change out, the second fluid may be a drilling fluid. It isbelieved that during normal leak off from the spacer fluids of thepresent invention into the subterranean formation, the hydrophobicallyand cationically modified relative permeability modifier, among otherthings, may attach to surfaces within the subterranean formation. Thepresence of the hydrophobically and cationically modified relativepermeability modifiers in the subterranean formation may reduce thepermeability of the treated sections of the subterranean formation toaqueous-based fluids (e.g., water) with little or no reduction in thepermeability of the subterranean formation with respect to hydrocarbons.This may reduce the subsequent problems associated with water flowinginto the well bore from the subterranean formation.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, theentire scope of the invention.

Example 1

In this example, the ability of a hydrophobically and cationicallymodified relative permeability modifier to remain in solution wasmeasured. A first fluid comprising a relative permeability modifier thatis not hydrophobically and cationically modified was prepared. The firstfluid comprised a 2000 ppm solution of polydimethylaminoethylmethacrylate (“polyDMAEMA”) reacted with 5 mole % hexadecyl bromide(“C16Br”). In addition, a second fluid comprising a hydrophobically andcationically modified relative permeability modifier was prepared. Thesecond fluid comprised a 2000 ppm solution of polyDMAEMA reacted with 5mole % C16Br and 5 mole % propyl iodide (“C3I”). Both of these fluidswere then heated to approximately 150° F. at pH of 8.6. It was observedthat the polyDMAEMA+C16Br present in the first fluid precipitated out ofsolution, while the polyDMAEMA+C16Br+C3I present in the second fluidremained in solution.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. While compositions and methods aredescribed in terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps. Allnumbers and ranges disclosed above may vary by some amount. Whenever anumerical range with a lower limit and an upper limit is disclosed, anynumber and any included range falling within the range is specificallydisclosed. In particular, every range of values (of the form, “fromabout a to about b,” or, equivalently, “from approximately a to b,” or,equivalently, “from approximately a-b”) disclosed herein is to beunderstood to set forth every number and range encompassed within thebroader range of values. Also, the terms in the claims have their plain,ordinary meaning unless otherwise explicitly and clearly defined by thepatentee. Moreover, the indefinite articles “a” or “an”, as used in theclaims, are defined herein to mean one or more than one of the elementthat it introduces. If there is any conflict in the usages of a word orterm in this specification and one or more patent or other documentsthat may be incorporated herein by reference, the definitions that areconsistent with this specification should be adopted.

1-20. (canceled)
 21. A method comprising: providing a relativepermeability modifier that comprises a hydrophilic polymer backbone witha hydrophobic modification wherein the hydrophilic polymer is selectedfrom the group consisting of: a polyacrylamide; a polyvinylamine; apoly(vinylamine/vinyl alcohol); an alkyl acrylate polymer; cellulose;chitosan; a polyamide; a polyetheramine; a polyhydroxyetheramine; apolylysine; a polysulfone; a gum; a starch; and a combination thereof;wherein the hydrophobic modification is achieved either by reacting thehydrophilic polymer with at least one hydrophobic compound or by apolymerization reaction product of a hydrophilic monomer and ahydrophobically modified hydrophilic monomer; wherein the hydrophobiccompound used for the hydrophobic modification comprises an alkyl chainlength of from about 4 to about 22 carbons selected from the groupconsisting of an alkyl acrylate; an alkyl methacrylate; an alkylacrylamide; an alkyl methacrylamide; an alkyl dimethylammoniumethylmethacrylate halide and any combination thereof; and, incorporating atleast one cationic compound onto the hydrophilic polymer backbone toform a hydrophobically and cationically modified relative permeabilitymodifier; wherein the cationic compound comprises at least one cationiccompound comprising an alkyl chain length of from about 1 to 3 carbonsselected from the group consisting of: an alkyl halide; a sulfone; asulfate; an organic acid; an organic acid derivative, and a combinationthereof.
 22. The method of claim 21, wherein the hydrophobicmodification is achieved by reacting the hydrophilic polymer with atleast one hydrophobic compound.
 23. The method of claim 21, wherein thehydrophobic modification is achieved by a polymerization reactionproduct of a hydrophilic monomer and a hydrophobically modifiedhydrophilic monomer.
 24. The method of claim 21, wherein the hydrophilicpolymer backbone comprises polar heteroatoms.
 25. The method of claim21, wherein the hydrophilic polymer backbone comprises amine groups. 26.The method of claim 23, wherein 1% to 20% of the amine groups present inthe hydrophilic polymer have been quaternized by the cationic compound.27. The method of claim 23, wherein 1% to 5% of the amine groups presentin the hydrophilic polymer have been quaternized by a hydrophobiccompound.
 28. The method of claim 21, wherein the hydrophilic polymercomprises at least one hydrophilic polymer selected from the groupconsisting of: a polyacrylamide; a polyvinylamine; apoly(vinylamine/vinyl alcohol); an alkyl acrylate polymer; cellulose;chitosan; a polyamide; a polyetheramine; a polyethyleneimine; apolyhydroxyetheramine; a polylysine; a polysulfone; a gum; a starch; anda combination thereof, and, wherein the hydrophobic compound comprisesat least one hydrophobic compound selected from the group consisting of:an alkyl acrylate; an alkyl methacrylate; an alkyl acrylamide; and acombination thereof.
 29. The method of claim 21, wherein thehydrophobically and cationically modified relative permeability modifiercomprises a mole ratio of cationic groups to hydrophobic groups in anamount in the range of from about 1:20 to about 50:1.
 30. The method ofclaim 21, wherein the relative permeability modifier comprises apolymerization reaction product of a hydrophilic monomer with ahydrophobically modified hydrophilic monomer, wherein the hydrophilicmonomer comprises at least one hydrophilic monomer selected from thegroup consisting of: acrylamide; 2-acrylamido-2-methyl propane sulfonicacid; N,N-dimethylacrylamide; vinyl pyrrolidone; dimethyl amino ethylmethacrylate; acrylic acid; dimethylaminopropylmethacrylamide; vinylamine; vinyl acetate; trimethylammoniumethyl methacrylate chloride;methacrylamide; hydroxyethyl acrylate; vinyl sulfonic acid; vinylphosphonic acid; methacrylic acid; vinyl caprolactam; N-vinylformamide;N,N-diallylacetamide; dimethyldiallyl ammonium halide; itaconic acid;styrene sulfonic acid; methacrylamidoethyltrimethyl ammonium halide; aquaternary salt derivative of acrylamide; a quaternary salt derivativeof acrylic acid; and a combination thereof; and, wherein thehydrophobically modified hydrophilic monomer comprises at least onehydrophobic ally modified hydrophilic monomer selected from the groupconsisting of: an alkyl acrylate; an alkyl methacrylate; an alkylacrylamide; an alkyl methacrylamide; an alkyl dimethylammoniumethylmethacrylate halide; an alkyl dimethylammoniumpropyl methacrylamidehalide; and a combination thereof.